1975 Laguna Tach wiring diagram

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1975 Laguna Tach wiring diagram

Post by RedonRedS-3 on Mon Nov 19, 2018 10:47 pm

I have done a search for diagrams, none for my specific year model.  I have the factory tach and gauge pack.  Looks like a brown wire with condensor on firewall coming from the HEI.  Comes through firewall at the accelerator then ends with GM single black plug.  I have a little black box dangling from the fuse box, says SW Stewart-Warner?  Has black wires(one cut) and pink I think.  Anyone have a diagram that would help, I would greatly appreciated.  Thanks
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Re: 1975 Laguna Tach wiring diagram

Post by g3chevy on Mon Nov 19, 2018 11:35 pm

Mine has the factory tach as well. The wire from the plug on the accelerator pedal bracket goes up to the main dash wire harness and then to the gauge cluster plug (see pic). It does not go through the fuse block. The "SW Stewart-Warner" box is most likely the key reminder buzzer. Hope this helps.

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Re: 1975 Laguna Tach wiring diagram

Post by RedonRedS-3 on Mon Nov 19, 2018 11:56 pm

Oh, I bet the buzzer was going off all the time...Hey you don't have a pic of that SW buzzer box? I have just about everything hooked up except for a couple connections. One green/white wire at the HEI with GM single black connector. Yellow/blk wire @ defrost vacuum diaphram's. And now the buzzer.
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Re: 1975 Laguna Tach wiring diagram

Post by g3chevy on Tue Nov 20, 2018 11:19 am

I'll see if I can get you a pic later today to shed some light on your wiring issues.
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Re: 1975 Laguna Tach wiring diagram

Post by Mcarlo77 on Tue Nov 20, 2018 5:24 pm

Probably a little late, but here is how your tach wire was routed from the factory as it passed thru the firewall.

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Re: 1975 Laguna Tach wiring diagram

Post by RedonRedS-3 on Tue Nov 20, 2018 7:41 pm

Oh no, never too late...That sheds some light on the situation...Those yellow wires throwed me off...Looks like I am missing something though...
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Re: 1975 Laguna Tach wiring diagram

Post by Mcarlo77 on Tue Nov 20, 2018 9:51 pm

One of those yellow wires runs to the Temp Control plug. The other one runs out thru the firewall and I think plugs into a switch on the backside of the block on passenger side along with yet another yellow wire. Can't remember what that switch is, however.
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Re: 1975 Laguna Tach wiring diagram

Post by RedonRedS-3 on Wed Nov 21, 2018 12:05 am



Anybody know where this green/wt wire went to?
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Re: 1975 Laguna Tach wiring diagram

Post by g3chevy on Wed Nov 21, 2018 1:28 am

That could be either the temperature sending wire or high idle solenoid wire that kicks the idle up when you turn on the a/c.
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Re: 1975 Laguna Tach wiring diagram

Post by Mcarlo77 on Wed Nov 21, 2018 11:41 am

I believe that grn/white wire feeds the A/C pigtail harness.
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Re: 1975 Laguna Tach wiring diagram

Post by RedonRedS-3 on Wed Nov 21, 2018 6:29 pm

A/C pigtail? Explain?
I wonder if my car had that idle up solenoid? If so, that bad boy is missing?
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Re: 1975 Laguna Tach wiring diagram

Post by g3chevy on Wed Nov 21, 2018 8:20 pm

I haven't been able to get over to my shop yet. But I should be over there tomorrow morning. I'll take some pics and post them to see if we can figure it out.
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Re: 1975 Laguna Tach wiring diagram

Post by Mcarlo77 on Wed Nov 21, 2018 8:34 pm

I should have said the pigtail harness that runs to the a/c compressor. I have a spare harness in a box that I'm using as reference. Just can't get to the Laguna until tomorrow to raise the hood and confirm.

As for the solenoid...I've never seen one of those on our "A" bodies during these years.  Certainly have on the full size cars, though.
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Re: 1975 Laguna Tach wiring diagram

Post by RedonRedS-3 on Wed Nov 21, 2018 9:29 pm




Top photo: this contraption just dangles from the fuse box, with one black lead cut...

The lower photo: also dangling from the dash, am I missing clips or something?
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Re: 1975 Laguna Tach wiring diagram

Post by Mcarlo77 on Wed Nov 21, 2018 10:04 pm

The buzzer in pic #2 pretty much just dangles.

As for your pic #1, I was comparing to my donor harness and it doesn't have that black box like shown in your photo.  Just has that white opaque plug with two black wires.  One wire plugs into the fuse box...other wire connects to a filter/condenser.  The filter would have been secured to the fuse box with a hex screw.  No idea what the box does, though...nor, why it's missing on my harness.  Here's my photo:

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Re: 1975 Laguna Tach wiring diagram

Post by RedonRedS-3 on Wed Nov 21, 2018 10:36 pm

Ah ha, yours is missing the black box, and mine is missing the filter...I think I have the filter somewhere, but the wire is broken off...Ok, getting somewhere...
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Re: 1975 Laguna Tach wiring diagram

Post by g3chevy on Thu Nov 22, 2018 12:31 am

Okay, your first photo is the headlight reminder buzzer. This came as part of the auxiliary lighting package which includes an under hood light, map light and truck light. I'm still not sure about the second photo. I've combed through my wiring schematic and can't find those color code wire combinations. You're welcome to look through these. Here are the pages in my 75 GM service manual. Also, here's a pic of the engine wiring harness I bought for my restoration. I couldn't find a green wire with white stripe so it must be part of the headlight wiring harness. The solid green wire is definitely for the temperature sending unit. But I'll check on my Laguna tomorrow. Hope this helps.





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Re: 1975 Laguna Tach wiring diagram

Post by RedonRedS-3 on Thu Nov 22, 2018 9:18 am

First pic, PWR HEAT VALVE SOLENOID/ OIL TEMP SW/ TEMP SW(MK)??? ALL DK GRN/WH STRIPE
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Re: 1975 Laguna Tach wiring diagram

Post by g3chevy on Thu Nov 22, 2018 11:55 am

That should be just for vehicles equipped with the 454 V-8 and 400 Turbo transmission. I remember those being on my 75 SS when I pulled the motor. More pics to follow shortly.
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Re: 1975 Laguna Tach wiring diagram

Post by Mcarlo77 on Thu Nov 22, 2018 5:01 pm

Ha...I popped the hood on the Laguna and it has that grn/white stripe wire dangling by the HEI, too. But, using my two spare underhood harnesses as reference, I am certain that connects to the wire harness that includes a connector for the A/C compressor and a plug for what I think is the temp sensor mounted into the block below the compressor. That pigtail harness also includes a ground wire that attaches to the compressor mtg bracket and a three-wire connector which I've yet to identify it's function.
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Re: 1975 Laguna Tach wiring diagram

Post by g3chevy on Thu Nov 22, 2018 7:56 pm

I second that. The plug with the green white stripe wire plugs into the A/C wire harness which is a solid green wire. Below is a pick of my Laguna with that plug setup. Also, here's a pic of the seat belt reminder buzzer and key reminder buzzer. Still not sure what the round cylinder is with the plug that has the yellow, pink, brown and black wire.

A/C Primary Plug



A/C Harness



Key Reminder Buzzer



Seat Belt Reminder Buzzer



Unknown Cylinder/Solenoid/Capacitor
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Re: 1975 Laguna Tach wiring diagram

Post by RedonRedS-3 on Sun Nov 25, 2018 9:39 pm



OK, I think I got the dongle buzzer fixed...

Now, where does this remaining ground strap located?

Oh, I was missing the seatbelt buzzer the whole time...Thanks Everyone for the great insight to my Laguna mystery's...
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Re: 1975 Laguna Tach wiring diagram

Post by RedonRedS-3 on Wed Nov 28, 2018 8:00 pm

Hey, G3Chevy...

Can you show a pic of the brown wires going to the buzzer or SW box? The brown wires are connected to fuse box(which location). I am missing the wires coming out of the SW box, I think...
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Re: 1975 Laguna Tach wiring diagram

Post by g3chevy on Fri Nov 30, 2018 1:13 pm

I'll see if I can get over to the shop this weekend and figure out the wiring and take a pic.
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Re: 1975 Laguna Tach wiring diagram

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